The long term o ject1ve objective of this rearch is to understand the effect of peripheral musculoskeletal injury on the sensorimotor organization of skilled movements and upon postura1 control during balance tasks. A group of highly trained dancers will be used in this investigation for two reasons. They exhibit highly consistent spatial and temporal coordination patterns while performing domain specific movements and have a musculoskeletal injury rate in excess of 40% per year. Specific ain1s include are: 1) To identity the effect of muscu1oskeletal injury and rehabilitation on the organization of skilled movements and postuies by comparing biomechanical parameters of movement before and after injury, after rehabilitation, and after return to fW1 activity; and 2) To determine the best method of evaluating function after injury by comparing different health status measures before and after injury and recovery. Specifically, we propose to compare the neuromuscular (electromyographic), kinematic, force platform, and health/functional status measures of uninjured, highly trained subjects while performing a series of skilled movements and postural tasks. The subjects will be followed prospectively for a period of three years. Subjects who sustain a musculoskeletal injury to the lower extremity or lumbosacral spine of sufficient severity will be reassessed while performing the test maneuvers immediately post injury, upon return to full activity, and three months after return. A set of matched control subjects will be recruited.. Comparisons between groups will be made to identify the adaptation of movement organization after injury and rehabilitation. The goal of this work is to understand the specific adaptations that occur in skilled movements following injury and rehabilitation so that we might design better rehabilitation programs for addressing loss of movement organization and clinical tools for identifying individuals at risk of injury.